Tunnel Vision—Excavating Subsea Roadways with Rugged Technology

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Workers who blast tunnels 290 meters below the ocean’s surface have plenty of "what-ifs" to consider. Technology failures and project budgets shouldn’t be among them. So contractors working on Norway’s Ryfast tunnel megaproject are using rugged mobile technology to ensure a reliable, safe and efficient excavation process that minimizes downtime and reduces personnel costs.

Crews are using the Amberg Navigator from Swiss company Amberg Technologies AG, a solution that packages Amberg Tunnel surveying software with Handheld Group’s Algiz 7 rugged tablet PC. The solution allows tunnel workers to take precise measurements, generate tunnel profile graphics in real-time, and compile detailed reports, eliminating the need for separate surveying crews. Best of all, workers can perform these tasks with no prior surveying experience and very little computer training time.

A tunnel beneath the sea
Norway’s west coast is made up of hundreds of small islands and fjords–areas where seawaters reach into narrow, deep valleys with high cliffs formed by glacial erosion. People traveling to and from the coastal city of Stavanger, the country’s fourth-largest metro and the hub of its offshore oil and gas industries, currently use bridges and ferries to access areas separated by water.

The new Ryfast tunnels will connect Stavanger to Norway’s Ryfylke region, replacing a ferry between the two areas and cutting travel time by two-thirds. One tunnel segment will link Stavanger’s Hundvåg borough to a small island called Hidle, and a second will connect Hidle to the town of Solbakk in Ryfylke.

Upon its 2018 completion, Ryfast will be the world’s longest, deepest subsea roadway tunnel, spanning 14.3 kilometers (8.9 miles) and reaching 291 meters (955 feet) below sea level at its deepest point. Swiss tunnel construction company Marti IAV Solbakk DA won a contract to build the Solbakk segment, which will include the tunnel’s deepest point. It will also feature a 7 percent gradient slope–the maximum tunnel gradient allowed.

A rugged technology breakthrough
To extend the tunnel through hard rock beneath the sea’s surface, Marti workers drill holes through the material in precise locations using enormous semi-automatic drill rigs. Explosives placed in those holes blast the rock away, and conveyor belts remove this material from the site.

Traditionally, hole placement for the "drill and blast" method of tunnel construction has been determined by surveying crews, who measure tunnel profiles and use this data to mark hole patterns or georeference drill rigs. But using the Amberg Navigator’s automated surveying software has eliminated the need for these extra surveyors; the tunneling crews themselves can quickly and easily perform surveying tasks with detailed real-time analysis.

"The Amberg Navigator helps avoid unnecessary waiting times because the measurements required can be integrated directly into the work procedures," says Jurgen Wilhelm, a Marti surveyor engineer. Of course, such highly precise work requires a reliable computer. For Solbakk tunnel workers, reliability means two things: adequate speed and memory to process profile data, and exceptional durability in tough environments.

The engineering challenges workers face in the tunnel are amplified by the frigid, wet environment where they perform their work. The tunnel’s surfaces can range from muddy and slippery to rough and jagged; temperatures can drop below freezing; and humidity, dust and potential drops all pose threats to ordinary technology. Every piece of equipment at the construction site must be able to withstand very harsh conditions.

With these requirements in mind, Amberg Technologies chose the Algiz 7 as the ideal complement to its Amberg Tunnel software. The Algiz 7 rugged tablet features a powerful Intel Atom processor, along with massive 128 GB storage capacity and 4 GB of DDR3 RAM. It runs Windows 7 Ultimate and compatible software, providing a seamless office-to-field experience.

The Algiz 7 also meets stringent MIL-STD-810G U.S. military standards for withstanding humidity, vibration, drops and extreme temperatures, and meets IP65 standards for sealing out dust and water. But despite its brawn, this rugged tablet is compact and portable, weighing only 1.1 kg (2.4 pounds). Its vivid 7-inch touchscreen displays data clearly, and 10 function buttons and an on-screen soft QWERTY keyboard make operation easy and intuitive.

A one-tablet control center
Jürgen Wilhelm, a Marti IAV Solbakk DA surveyor engineer on the Ryfast tunnel project.

With the Amberg Navigator, crews can measure tunnel profile data quickly and easily, display visualizations of that data in real time, and save detailed data logs. This solution is extremely simple to use, even without any previous knowledge of surveying. The software automates all measuring tasks, which workers can select and manage with one touch by tapping large, easy-to-interpret icons with illustrations.

"Workers can control and verify an entire tunnel project with a single tablet," says Oliver Schneider, Amberg Technologies product manager.

To take measurements, workers use a total station–an electro-optical scanning tool that measures angles, distances and coordinates. They position the total station on a tripod or console aimed toward the area to be measured. Then the Amberg Navigator communicates with the total station using Bluetooth, automatically adjusts the total station’s viewing area, and initiates profile data collection.

The Navigator can automatically profile a tunnel at pre-defined stations; it highlights areas where a blast has taken away too much or too little material; and it evaluates surface-layer thickness and displays the data graphically on the screen. With this information, workers can use the Navigator to set precise blast patterns and control drilling machinery.

"The rugged tablet makes it possible for personnel from other sectors to carry out simple, routine surveying tasks reliably, efficiently and independently," Wilhelm says. Smart solutions from Handheld and Amberg are helping the Ryfast project progress smoothly and efficiently. And that’s a good thing, because subsea construction workers have much better ways to spend their time than waiting around.

Brynna King is a freelance writer and editor based in Portland, Oregon. She can be reached at Word Jones, www.wordjones.com.

A 4.904Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE